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From: Rusty Russell <rusty@rustcorp.com.au>
To: Ingo Molnar <mingo@elte.hu>
Subject: Re: [patch 7/9] LTTng instrumentation - kernel
Date: Wed, 25 Mar 2009 11:43:11 +1030
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Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
       ltt-dev@lists.casi.polymtl.ca, Frederic Weisbecker <fweisbec@gmail.com>,
       Masami Hiramatsu <mhiramat@redhat.com>,
       Peter Zijlstra <peterz@infradead.org>,
       "Frank Ch. Eigler" <fche@redhat.com>, Hideo AOKI <haoki@redhat.com>,
       Takashi Nishiie <t-nishiie@np.css.fujitsu.com>,
       Steven Rostedt <rostedt@goodmis.org>,
       "Eduard - Gabriel Munteanu" <eduard.munteanu@linux360.ro>
References: <20090324155625.420966314@polymtl.ca> <20090324160148.872305963@polymtl.ca> <20090324183313.GH31117@elte.hu>
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On Wednesday 25 March 2009 05:03:13 Ingo Molnar wrote:
> 
> (Rusty Cc:-ed - for the module.c tracepoints below)

Thanks, tho they look fine and non-intrusive to me.

> I believe that to have a complete picture of module usage, module 
> refcount get/put events should be included as well, beyond the basic 
> load/free events.
> 
> These both have performance impact (a module get/put in a fastpath 
> hurts scalability), and are informative in terms of establishing the 
> module dependency graph.

A module_get()/put() should not hurt scalability at all!  I went to great and
horrible lengths to ensure that was the case since the rewrite in 2.4.

But a module dependency graph et. al. would be kind of cool.

Thanks,
Rusty.